Professional radios are enormously expensive to rent. Not so much for the hardware, but because one must pay someone to rent the airwaves. Professional quality radio communications are basically carried on a cellular or other large provider owned network.
With that unaffordable to grass roots rides, I've done some broad research leading to practical recommendation for a balanced solution to future live ride communications solution:

Carry the most powerful legally available radios for short distance voice communications, especially among safety/green/etc team members. We use 5W (36mi) GRMS.

Interconnect as many iPhone using key parties as possible on the built-in Find My Friends app, no installation required, just invite each other. This securely and intuitively allows one to see several friends locations mapped in real time.

Use GroupMe for routine text chatter (ie. nerds). Just like Chiditarod, we already have an account. Work even with basic phones.

Ideally add an "operator" at a central number helping with communications. They could easily do things like manage an open conference call and handle emerging and urgent situations. A Google voice number could be used.

Smartphone PTT Apps:
Several "Push To Talk" radio simulating apps are available for smartphones, and compatible across all common makes and models. There's a review of the best here. In 2013 we tried Voxer. Voxer features real-time push-to-talk, also push notifications, message queuing, GPS, photo and text capabilities, but has a limit on users at the free level, and requires smartphones. Similar apps had similar limits.

GMRS:[wikipedia]
General Mobile Radio Service is an FM system in the 462MHz range (shared with FRS). Allowed power up to 5W. Requires a simple license in U.S. Channels 1-7 are solely for use with the FRS/GMRS system. Channels 8-14 are solely for FRS and 15-22 is for GMRS. Depending on terrain, these radios can have a much broader range than FRS, possibly extending a few miles.FRS:[wikipedia]
The Family Radio Service provides a series of 14 channels in the 462 and 467 MHz range. Using frequencies in the UHF band, and FM, gives less interference than CBs. These radios require no special license, but are low power and short ranged.PMR:[wikipedia]
Professional Mobile Radio / Private Mobile Radio and land mobile radio (LMR) are field radio communications systems which use portable, mobile, base station, and dispatch console radios. Operation of PMR radio equipment is based on various advanced standards, designed for dedicated use by specific organizations, or for general commercial use. Typical examples are the radio systems used by police forces and fire brigades. Professional mobile radio systems provide large coverage area using base station, tower, repeater or cell systems. Stringent licensing is required.FHSS:[wikipedia]
Frequency Hopping Spread Spectrum combines digital technology with narrow band FM modulation technique in the ISM band (900 MHz frequencies). Ensure for maximum usable range within a given dB power budget with the added benefit privacy provided by the frequency hopping spread spectrum algorithm. The pseudo-random drawing of the hopping frequencies spreads the total signal power equally over the entire bandwidth of the RF spectrum used, which minimizes interference between simultaneous independent users. Under identical conditions FHSS will have usable talk range equal to or greater than other GMRS radios. Requires no license and can be used at any age and for any purpose.CB:[wikipedia]
Citizens Band is a largely obsolete, now hobbyist and specialty standard, functionally overlapping GMRS, but capable of longer distance through large antennas and illegal amplifiers. 40 Channels, 4 watts, 26.965-27.405 MHz, 162.400-162.550 MHz, AM modulation. The maximum legal CB power output level, in the U.S., is four watts for AM and 12 watts (peak envelope power or "PEP") for SSB, as measured at the antenna connection on the back of the radio. Although licenses are required, eligibility is simple.

Practical comparison: Highest legal power GMRS and FHSS radios found identical range (just over a mile straight), though FHSS was slightly less static-y nearing maximum distance. In testing, straight line (though on a hilly street), voice was VERY clear on both at half a mile, still very intelligible at 3/4, still usable at one mile, unintelligible at 1.2 miles, and no signal at all after 1.3 miles. Worse still, the slightest angle, where signal would have to pass through buildings, radically lessened the distance. At just one block over from straight line, voice was usable at a half mile or closer, but became unintelligible only slightly further.Real World Ranges: For CB, FRS, GMRS and MURS Radios.